P
US6927926B2ExpiredUtilityPatentIndex 74

Telephoto lens and telephoto lens apparatus having the same

Assignee: OLYMPUS CORPPriority: Apr 22, 2002Filed: Apr 15, 2003Granted: Aug 9, 2005
Est. expiryApr 22, 2022(expired)· nominal 20-yr term from priority
Inventors:KASAHARA TAKASHIIMAMURA MASAHIRO
G02B 13/02
74
PatentIndex Score
8
Cited by
6
References
21
Claims

Abstract

A telephoto lens includes, in order from the object side, a first lens unit having a positive refracting power, a second lens unit having a negative refracting power, a third lens unit having a positive refracting power, and a fourth lens unit having a negative refracting power. The second lens unit has a cemented lens composed of a positive lens and a negative lens, and a negative lens. The fourth lens unit has a cemented lens composed of a negative lens and a positive lens, and a negative lens. The telephoto lens satisfies the following conditions: ν d >80 −0.5> f 4 /f >−1.2 where ν d is an Abbe's number of a lens having a positive refracting power in the first lens unit, f 4 is a focal length of the fourth lens unit, and f is a focal length of the entire optical system.

Claims

exact text as granted — not AI-modified
1. A telephoto lens comprising, in order from an object side:
 a first lens unit having a positive refracting power;  
 a second lens unit having a negative refracting power;  
 a third lens unit having a positive refracting power; and  
 a fourth lens unit having a negative refracting power,  
 wherein the second lens unit comprises a cemented lens composed of a positive lens and a negative lens, and a negative lens,  
 wherein the fourth lens unit comprises a cemented lens composed of a negative lens and a positive lens, and a negative lens, and  
 wherein the telephoto lens satisfies the following conditions 
   ν d >8  
   0.5>ƒ 4 /ƒ>−1.2  
 
 
     where ν d  is an Abbe's number of a lens having a positive refracting power in the first lens unit,ƒ 4  is a focal length of the fourth lens unit, and ƒis a focal length of an entire optical system. 
   
   
     2. A telephoto lens according to  claim 1 , wherein the following condition is satisfied:
   n d1 −n d2 >0.2  
 
     wherein n d1  is a refractive index of the positive lens and n d2  is a refractive index of the negative lens, in the cemented lens in the fourth lens unit. 
   
   
     3. A telephoto lens comprising, in order from an object side:
 a first lens unit having a positive refracting power;  
 a second lens unit having a negative refracting power;  
 a third lens unit having a positive refracting power; and  
 a fourth lens unit having a negative refracting power,  
 wherein the first lens unit consists of two positive lenses and two negative lenses.  
 
   
   
     4. A telephoto lens according to  claim 3 , wherein the first lens unit consists of, in order from the object side, a negative lens, two positive lenses, and a negative lens. 
   
   
     5. A telephoto lens according to any one of claims  1  through  4 , wherein a configuration is made so that, in focusing toward a proximity, the second lens unit and the fourth lens unit are moved toward an image side. 
   
   
     6. A telephoto lens according to any one of claims  1  through  4 , wherein the fourth lens unit comprises a cemented lens composed of a positive lens and a negative lens, and a negative meniscus lens. 
   
   
     7. A telephoto lens according to any one of claims  1  through  4 , wherein the following condition is satisfied:
   10.0 mm>y>13.0mm  
 
     where Y is a diagonal length of a picture surface. 
   
   
     8. A telephoto lens according to  claim 1  or  2 , wherein the first lens unit comprises a plurality of lenses each having a positive refracting power, of which lenses a plurality of lenses satisfy the following condition:
   ν d >80  
 
     where ν d  is an Abbe's number of a lens having a positive refracting power in the first lens unit. 
   
   
     9. A telephoto lens according to any one of claims  1  through  4 , wherein each lens having a positive refracting power included in the first unit satisfies the following condition:
   85 >ν d >80  
 
     where ν d  is an Abbe's number of a lens having a positive refracting power in the first lens unit. 
   
   
     10. A telephoto lens according to any one of claims  1  through  4 , wherein the following condition is satisfied:
   −0.6 >f    4    /f >−1.1  
 
     where ƒ 4  is a focal length of the fourth lens unit, and f is a focal length of an entire optical system. 
   
   
     11. A telephoto lens according to  claim 3  or  4 , wherein the fourth lens unit comprises a cemented lens composed of a negative lens and a positive lens, and the following condition is satisfied:
   n d1 −n d2 >0.2  
 
     where n d1  is a refractive index of the positive lens and n d2  is a refractive index of the negative lens, in the cemented lens in the fourth lens unit. 
   
   
     12. A telephoto lens according to any one of claims  2  through  4 , wherein the following condition is satisfied:
   0.5>n d1 −n d2 0.2  
 
     where n d1  is a refractive index of the positive lens and n d2  is a refractive index of the negative lens, in the cemented lens in the fourth lens unit. 
   
   
     13. A telephoto lens according to any one of claims  1  through  4 , wherein a configuration is made so that, in focusing toward a proximity, at least the first lens unit is fixed and the second lens unit is moved toward an image side. 
   
   
     14. A telephoto lens according to any one of claims  1  through  4 , wherein a configuration is made so that, in focusing toward a proximity, the second lens unit is moved toward an image side and the third lens unit is moved toward the object side. 
   
   
     15. A telephoto lens according to  claim 5 , wherein a configuration is made so that, in focusing toward the proximity, the first lens unit and the third lens unit are fixed. 
   
   
     16. A telephoto lens according to  claim 14 , wherein a configuration is made so that, in focusing toward the proximity, the first lens unit and the fourth lens unit are fixed. 
   
   
     17. A telephoto lens according to any one of claims  1  through  4 , wherein a photographing half-field angle is in a range from 10.0° to 0.50. 
   
   
     18. A telephoto lens according to any one of claims  1  through  4 , wherein the second lens unit consists of, in order from the object side, a cemented lens composed of a positive lens and a negative lens, and a negative lens. 
   
   
     19. A telephoto lens according to any one of claims  1  through  4 , wherein the fourth lens unit consists of, in order from the object side, a cemented lens composed of a negative lens and a positive lens, and a negative lens. 
   
   
     20. A telephoto lens apparatus comprising a telephoto lens, the telephoto lens comprising, in order from an object side:
 a first lens unit having a positive refracting power;  
 a second lens unit having a negative refracting power;  
 a third lens unit having a positive refracting power; and  
 a fourth lens unit having a negative refracting power,  
 wherein the telephoto lens has a lens mount section that is connectable with a camera on an image side,  
 wherein the second lens unit comprises a cemented lens composed of a positive lens and a negative lens, and a negative lens,  
 wherein the fourth lens unit comprises a cemented lens composed of a negative lens and a positive lens, and a negative lens, and  
 wherein the telephoto lens satisfies the following conditions 
   ν d  >80  
   −0.5 >f   4   /f >−1.2  
 
 
     where ν d  is an Abbe's number of a lens having a positive refracting power in the first lens unit, f  4  is a focal length of the fourth lens unit, and f is a focal length of an entire optical system. 
   
   
     21. A telephoto lens comprising, in order from an object side:
 a first lens unit having a positive refracting power;  
 a second lens unit having a negative refracting power;  
 a third lens unit having a positive refracting power; and  
 a fourth lens unit having a negative refracting power,  
 wherein the first lens unit consists of at least two positive lenses and two negative lenses, and  
 wherein none of the lenses in the first lens unit are cemented.

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